The present invention relates to apparatus for loading semiconductor wafers into an oven for atmospheric pressure processing.
A variety of semiconductor processing operations are commonly performed in diffusion furnaces. Semiconductor wafers are typically subjected to high temperatures and a particular gas mixture in the furnace. A typical furnace configuration will be a stack of four tubes, each of which can receive, from an open end, a tray or "boat(s)" of disk-shaped semiconductor wafers. The closed end of the furnace tube will typically have piping coupled to it for injecting the appropriate gasses for the operation to be conducted. The opened end of the furnace tube extends into a "scavenger box" which is in an area to which a vacuum is applied to remove the reactant gasses.
In one method of loading the boat(s) of wafers into the furnace, a pair of cantilever rods or a paddle holding the boat(s) is extended into the furnace and subsequently removed with a motor driving the rods.
After the processing of the wafers in the furnace, it is desirable to have a controlled cool down cycle for the wafers while exposing them to an inert gas. One method of doing this is to use a tube which encloses the wafer boat(s). This tube is extended into the furnace with the boat(s) on the cantilever rods. After processing, inert gasses are driven through the furnace and tube, and the boat(s) and tube are removed so that the tube extends outside of the furnace, but overlaps with the furnace enough to prevent outside air from entering the tube. By moving the wafer boat(s) out of the furnace, it can cool more quickly and is not limited by the cooling time of the furnace heating elements. A protective tube prevents oxygen from contacting the wafers during this cooling period. If oxygen were to contact the semiconductor wafers while they were still hot, an undesirable oxidation of the wafers would occur.
Necessarily, the tube covering the wafers must be able to withstand the high heats of the furnace and the furnace will need a large opening to accommodate the tube. In addition, the purge tube must be able to be subjected to the variety of gasses used in the furnace.